Networks of devices that connect machines to the Internet are becoming increasingly popular. Commonly such networks are known as IoT (Internet-of-Things) networks. Within an IoT network, IoT nodes (which are very often battery powered) typically measure physical values (such as a temperature, or a number of items, for example), and then either: store the value(s) locally; transmit the value(s) to the Internet; analyze the value and make a local decision if an action is required based on the value(s), and if the action must be reported to the Internet; or any combination of the above.
IoT networks have a few important characteristics. They must be able to operate over a very long range, and must be able to operate with very low power consumption.
A number of different network technologies are currently being used to deploy IoT networks. These include LoRa, SigFox, LTE CAT-M1 and NB-IoT. These networks have been specifically designed to address the two characteristics noted above. Also, the network types can be split into two broad categories, namely cellular-based systems and other systems. Cellular systems include LTE CAT-M1 and NB-IOT systems, and are characterized by the use of cellular networking standards and technologies to implement the IOT networks, and which are the focus of this document.
One aspect related to a cellular network base station is that the network is always ON. Typically the base station is always transmitting common control and pilot channels in the downlink direction, even if there is no uplink traffic present. This allows for user devices to be contactable at any time and, conversely, for user devices to be able to send messages via the base station at any time. Normally this is the desired behavior for a cellular system. Even in the case of an IoT system that either shares common cellular networking infrastructure with normal cellular traffic, or in the case of purposefully built IoT cellular system, this is generally the desired behavior as the coverage area of such a system is very large, and thousands of devices can be addressable in the coverage area of the base station via the network.
However, even with the large coverage area provided by cellular base stations, it is well known that coverage is often inadequate due to either distance from the base station or due to signal propagation impairment by walls and buildings.